Timing Gear Marks not Aligned - JeepForum.com

 
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post #1 of 10 Old 10-27-2012, 09:41 AM Thread Starter
nfisher50
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Timing Gear Marks not Aligned

I replaced my timing chain and found that the timing marks were not aligned like you typically see. Mine are 180 from each other. The jeep ran fine before, but I had about 1/2" of slack and replaced it to help determine if this is the problem for my timing jumping around.

I have a comp cam upgrade which maybe why this is like this? I did set the #1 at TDC on the compression stroke. So my question is this is a correct install right?

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post #2 of 10 Old 11-03-2012, 09:26 AM
Timido
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if you turn the crank one more time around I bet the marks line up. You were on #1 TDC but you were probably on the Exhaust stroke. When I set up TDC I turn the engine over and watch the #1 intake valve when it opens and closes just after that is TDC compression stroke.
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post #3 of 10 Old 11-03-2012, 07:22 PM Thread Starter
nfisher50
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I'll double check that. While I'm at all this, I bought a degree wheel and found that my timing cover and harmonic balancer do not add up to TDC at the 0 mark. It was off 2*. I checked my cam and the intake center line is at 108.5 but my comp cam card says it should be at 106. I've checked this several times and am taking a dial measurement straight off the pushrod (ie: not using the springs or rocker arms) however I am still using the hydraulic lifters. I've waited several minutes inbetween measurements to make sure the hydraulic pressure has bleed down. I've read several articles that state if the cam is off I need special bushings or offset woodruff keys, but why can I not just rotate the cam gear a tooth up or down on the chain and recheck?
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post #4 of 10 Old 11-03-2012, 08:24 PM
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I would Set the cam up with the timing marks. I would think a tooth off would be alot more than 2 degrees. Top dead center being off could be because of machining on the pulley and the cover and chain stretch. If you have the head off I could tell you how to set and check your dampener and pointer to make sure they are correct.
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post #5 of 10 Old 11-03-2012, 08:29 PM
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Quote:
Originally Posted by Timido View Post
if you turn the crank one more time around I bet the marks line up. You were on #1 TDC but you were probably on the Exhaust stroke. When I set up TDC I turn the engine over and watch the #1 intake valve when it opens and closes just after that is TDC compression stroke.
This.

Don't forget that because of the size difference, the camshaft rotates twice for every rotation of the crankshaft.

Because it's 180* off, it just means that it's on the exhaust stroke. Did you check your distributor position to make sure it was pointed at the cylinder 1 wire?

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post #6 of 10 Old 11-03-2012, 08:32 PM Thread Starter
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Yes it was at the #1, although several degrees past the #1 plug wire.
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post #7 of 10 Old 11-03-2012, 08:34 PM
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Also, the harmonic balancer can actually independently get spun as it ages, making it not align with the timing marks the way it's supposed to.

If you're suspicious of yours, the best way to gauge TDC is by the screw-driver-in-the-sparkplug-hole trick.

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post #8 of 10 Old 11-04-2012, 06:32 AM Thread Starter
nfisher50
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To find TDC I made a piston stop that bolted to the block.

So what I was trying to figure out is can I rotate the cam a tooth forward or back?
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post #9 of 10 Old 11-08-2012, 11:26 AM
muddy93
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[QUOTE=CrawlingForward;14400747]

Don't forget that because of the size difference, the camshaft rotates twice for every rotation of the crankshaft.
QUOTE]

you have that backwards. The crankshaft is the one that turns faster.

Quote: "To find TDC I made a piston stop that bolted to the block."
are you sure that you were on the compression stroke though? The piston comes to TDC between the compression and power strokes, and then again between the exhaust and intake strokes. If you are at TDC between the exhaust and intake, the timing marks will be off.

EDIT:
Looking again at the picture in post #1, If you turn the crank one full revolution, the cam gear will make 1/2 revolution, which will put your marks in line. This makes me think that you have the #1 piston at TDC between the exhaust and intake strokes.

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post #10 of 10 Old 11-08-2012, 11:38 AM
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Quote:
Originally Posted by muddy93 View Post
you have that backwards. The crankshaft is the one that turns faster.
Ah, thank you! I always have trouble remembering which duplicates.

The thing that helps me remember and may help the OP understand as well:

The cam shaft does one rotation because each cam lobe has a unique task, i.e. opening a valve or closing a valve, and only performs that function once per camshaft rotation.

The crankshaft, however, rotates twice per revolution of the camshaft because each cylinder has to cycle twice, once for compression/ignition and once for exhaust/intake, before the camshaft is done performing all valve opening/closings.

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